Fan with rubber blades



Nov. 2, 1937. E. s. PRESTON v 2,098,107

FAN WITH RUBBER BLADES Filed Aug. 22, 1936 *2 Sheets-Sheet l Nov. 2, 1937. E. s. PRESTON 2,098,107

FAN WITH RUBBER BLADES Filed Aug. 22, 1956 2 Sheets-Sheet 2 Patented Nov. 2, 1937 2,098,107 FAN VVIIICH RUBBER BLADES Edward S. Preston, Chicago, 111., assignor to Chicago Electric Manufacturing Company,

Chi-

cago, 111., a corporation of Illinois Application August 22, 1936, Serial No. 97,318

17 Claims. (Cl. 230-261) My invention relates to a rotatable and bladed fan member, designed for blowing air away from the end of a shaft to which it is attached, and

suitable for use in household and oflice types ofv 5, electric fans. I

In general, the objects of my invention are those of providing an inexpensive and easily manufactured fan member of this class in which the blades are integralwith each other and cut from a sheet of flexible rubber or the like, and in which the blade assembly somewhat simulates that of a toy pin-wheel, butin which the blades are so differently shaped and mounted as to be far more efiicient than those of a toy pin-wheel. In addition, my invention aims to shape the blades so that they will not present sharp tips, such as might injure a hand engaging the blades whilethe bladed fan motor is rotating, and so that the tip portions of the blades can temporarily be flexed by such an "engagement with a hand without damaging the blades or loosening any blade part from its mounting. Furthermore, my invention aims to provide simple and easily assembled means for maintaining a flexible multi-blade part of a fan member in its operative shape and for supporting that member on a rotating shaft, which means will include a forward element shaped so as to aid in having the fan spread the propelled air with fair uniformity over a considerable cone angle.

Illustrative of the mannerin which I'accomplish the above recited objects,

v Fig. 1 is a front elevation of r a flexible-bladed fan member embodying my invention, and'Flg. 2 is a side elevation of the same.

Fig. 3 is'a rear elevation, drawn on a reduced scale.

Fig. 4 is a side elevation, similar to Fig. 2 but with the major portions of the iiexible member broken away. Fig. 5 is a section taken through Fig. 4 along the line 5-5.,

Fig. 6 is a plan view of the blanked piece of sheet rubber as it appears before it is bent to present the partially scoop-like blades of Figs. 1 to 3 and'attached to the metallic clamping and supporting means shown in Figs. 4 and 5, drawn on the same scale as Figs. 1 and 2; and Figure! is a view similar to Figure 5 but showing a slight a modification. V

In manufacturingmy fan-blade unit I first provide a blade-forming blank, cut from a sheet of moderately flexible rubber and shaped as shown in Fig. 6. This blank has a central perforation l and also has a plurality of radial slits l5 extending into it for dividing the part of the'blank outside of a central imaginary circle C into counterpart wings adapted to form the fan blades. For the illustrated four-blade fan, two of the said slits will be in a common plane dia- 5 metric of the said central perforation and the other two. in a second diametric plane at right angles to the aforesaid plane, as shown in Fig. 6. Each wing of the blank desirably is formed so that the wing edge L which is to be the leading 10 edge of the corresponding blade is straight except for a relatively short free end portion L This curved blade tip portion merges into acurved edge portion E which (in a four-wing blank) may be approximately one longitudinal it half of a semi-circle 3 of which the straight edge portion L is diametric. In additionto this generally semi-circular main blade-forming portion, each wing of the blank includes a strap portion S which increases in width toward the said semi- 2o circle" and which has a perforation 4 nearits free end. The part of this strapportion near its 1 free end has its free edge extending along a slit l5 at right angles to the edge L of the wing,

while the more radially inward portion A of the said free edge of the strap is desirably concaved as shown in Fig. 6 to permit a more ready flexing of the strap, and this concaved edge portion desirably is considerably longer than the said straight free edge portion. 30

Then I provide an assemblage for supporting the rubber blank with its wings distorted to constitute blades, for connecting the resulting four- ,bladed' fan element to a rotatable shaft, and for preventing the creation of a vacuum in front 35 of the axis of the fan, as shown in Figs. 4 and 5. The longest constituent of this assemblage is a stem member comprising a forward stem portion la adapted to extend slidably through the central perforation l in the. rubber blank and also 4 through the strap perforations 4 when the straps have consecutively been bent forwardly and thereafter toward each other to aline all of the strap perforations with the said central perforation. 45

line said stem member has its rear end portion lb 'of considerably larger diameter than its said forward portion, and has an axial bore 8 extending into its rear end for receiving a rotatable shaft 9 (shown in dotted lines in Fig. 5) to which that member may be clamped by a set screw it. In addition, this. stem member includes a diametric enlargement adjacent to the juncture of Y its said parts la and lb, here shown as consistin of a metal washer ll slid over the smaller diametered stem part "la and bearing rearwardly against the forward end of the larger diametered rear stem part lb. This washer is desirably of the same diameter as the central circular portion C of the rubber blank (Fig. 6) at which the slits in this blank have their inner ends, and in the hereafter described assemblage of said washer ll operatively forms a peripheral flange part of the stem member.

Next I provide a spacer E3 of smaller diameter than the said washer, which spacer isbored to flt over the forward stem part Ta and is of a height suitable for properly spacing the free end portions of the overlapped straps of the wings of the rubber blank forwardly from the central portion of that blank. Then I also pro:

vide a nut i4 attachable to the threaded forward end of the stem member for clamping the said strapend portions against the said spacer, this nut being desirably a cap nut formed for cooperating with the fan blades in effectively distributing the air which is blown forwardly by the fan. To lighten and cheapen this spacer I desirably form it as a metal cap which has its head I301. centrally perforated so that the forward stem part Ia can slide through it, and which has a peripheral flange I3b at its rear end to present an enlarged bearing area to the part of the rubber blank against which the rear end of the spacer bears.

In assembling my bladed fan unit, the washer II is first slid over the forward stem part lo and against the annular shoulder 1c at the juncture of that stem part with the larger diametered rearward part lb, and this forward stem part is then slid through the central perforation I in the rubber blank to seat that blank on the washer. The spacer I3 is next slid over the forward stem part to seat on the rubber blank, after which the straps S of the several wings of that blank areconsecutively bent so as to have the stem part "la slide consecutively through the perforation I in each ofthe straps. Then the attaching of the cap nut clamps the washer, the central blank portion, the spacer and the overlapping ends of the four straps an between that nut and the said shoulder 10 of the stem member to constitute a rigidlyassembled unit.

During such an assembling, the free ends of the four straps necessarily are at different forward spacings from, the central portionof the bladed rubber blank, both when these strap ends,

are attached in rotationally 1--32--4 order. However, when the grade of rubber is such as to permit the rubber element to be suitably thin-'- as for example less than one-sixteenth inch thick,

I have found the resulting variations in the blade shapings to be immaterial because the flexibility of the rubber permits themto re p nd to the air pressure'in such a manner as to effectively equalize the shape of the main blade portions when my fan member is rotating at a" considerable speed. To facilitate this I preferably make the width of each strap end portion a quite small fraction of the radial blade length in the rubber blank, as for examfie not over one-fifth of that length. 1 w

During such rotation, the back pressure on each of the blade parts which are visible from the front, as in Fig. 1, together with" the rotational pressure (along the line, of the arrow a in Fig. 1) against the interior of the U-back of each bl de, tend to flatten the said frontally visible part of the blade which propels the air for- However, part of the air scooped by.

each blade also flows toward the inner end portion of the next rotationally rearward blade where it encounters similarly inwardly moving air passing behind the strap on the latter blade.

By extending the arcuate trailing edgeE of each blade beyond the mid-length of each blade before it merges with the strap portion of that blade and making the width of the strap a small fraction of the total length of the blade I make each strap so flexiblea's to permit a more ready flexing of the outer edge of each blade part than would occur if that edge was a straight line (as in a toy paper pinwheel) or if the said edge was a 90'degree arc of a circle.

When my fan member is rapidly rotating, the clamping nut l4 eliminates the creation of a vacuum adjacent to the axis of this member and also appears to aid in somewhat redirecting the air which flows past the exterior of the said nut, so as to spread the propelled air into a cone instead of having the air propelled as a concentrated beam of undesirably small diameter. Consequently, I have found that with the here illustrated fan member, the projected air spreads over a cone angle of approximately'40 degrees, with a fairly uniform velocity throughout this spread, and that at a rotational speed of 1000 or 1200 such a fan is practically silent in operation.

Moreover, the above described relatively narrow width of the strap portion of each blade also allows the tip of a blade, and indeed the entire radially outward half of the length of a blade,

to be bent rotationally rearward if it impacts against any object, so that my fan blade member can be halted by thrusting a hand against through it.

Furthermore, if the rubber in my bladed mem-' ber deteriorates in the course of years, a new member. can readily be attached to the same electric fan by any user, which cannot be done with the customary fans in which the wire guard is attached to the motor casing by rivets. So also,

the elimination of the heretofore required wire guard compensates for the higher cost of my fan blade member in comparison with the all-metal types now in common use, so that I am able to.

obtain all of my above recited advantages without an increase in cost. "In addition, the elimination of the need of a wire guard reduces the size "of carton required for packing the entire electric fan, and the flexibility of the rubber, blades eliminates the distorting of metal fan blades which so often occurs in transit and otherwise through rough handling.

.still permit the fingers of a ,child to reach.

However, while I have heretofore describedmy invention in connection with a. fours-bladed might be made either in these or other without. departing either from the spirit of, my invention or from the appended claims.

embodiment and one in which the spacer is'o'f 7 a cap form, it will be obvious that many changesedge concaved.

near the outer end of its rotationally rearward edge portion, the said wings being all bent forwardly and thereafter radially inwardly to dispose their said end portions in relatively overlapping relation and to have the said wing perforations aline with the central perforation in the said sheet; a stem extending forwardly through all of the said perforations; a spacer sleeved upon and centered by the stem'member and disposed between the said sheet and the said overlapped wing portions; and means associated with the said stem memberconjointly clamping the said wing portions, the spacer and thecentral sheet portion rearwardly against a portion of the stem member.

2. A pin-wheel type fan member as perfclaim 1, in which the said means comprise a forwardly tapering conoidal cap nut threaded upon the forward end of the stem member and bearing rearwardly against the most forward of the said overlapping wing end portions.

3. A pin-wheel type fan member as per claim 1, in which each wing is generally shaped as a semicircle having its .diametric side forming the leading edge of the wing, and in which said straps extend radially of the fan member alongside the trailing edge of the wing, the width of the strap being less than one-fourth the diameter of the said semi-circle and the wing perforation being formed in the said strap.

4. A pin-wheel type fan member asper claim 1, in which each wing comprises a main wing part generally shaped as a semi-circle having its diametric side forming the leading edge of the wing, and in which said straps extend away from the center of the said sheet along the fan member at the trailing edge of the wing; thes'aid strap having the radially inward portion of its said trailing 5. In a rotatable fan-blade unit, a fan-blade element comprising a centrally perforated blade sheet of flexible rubber having equally spaced slits extending radially into it, the said slits defining edges of counterpart wings each comprising a curved trailing edge, and each presenting a strap-like end portion adjacent to one of the slits, and atthe trailing edge of its wing the said strap-like portionsv being adjacent to the similarly facing wing edges and each'wing having a perforation near the free end of its trailing edge,

and the said wings being bent forwardly to present the free end portions of the said straps in relatively overlapping positions in which the perforations in the straps aline axially with the central perforation in the said sheet; a centrally perforated spacer member disposedbetween the inner of the said overlapping strapl ike portions and the central portion of the said sheet; a stem member extending through the said central perforation in the sheet, the spacer member and the perforations in the said strap-like portions; and means associated with the steminember and attachable at its rear end .to a shaft for clamping the spacer member and the said central sheet porforming part of the stem member and engaging the rear face of the said sheet, and a nut threaded -upon the forward end of the stem member and bearing rearwardly against the outer of the said overlapping strap-like portions.

'7. A fan-blade unit as per claim 5, in which the said clamping means comprise a peripheral flange forming part of the stem member and engaging the rear face of the said sheet, and a nut threaded upon the forward end of the stem member and bearing rearwardly against the outer of the said overlapping "strap-like portions; the spacer being a rigid and rearwardly open-cap having its rear end provided with a peripheral flange bearing against the said sheet.

8. A fan-blade unit as per claim 5, in'which each blade-forming wing of the said sheet, before its strap portion is bent forwardly, is of the general shape of a semi-circle having one of the said slits as its base line and having its strap portion projecting from inner portion of the wing and contiguous to the next slit in the sheet.

9. A fan-blade unit as per claim'5, in which the edge of each strap-like portion which is adjacent to a slit comprises a straight part near the end of part.

10. A fan-blade unit as per claim 5, in which the edge of each strap-like portion which is ad-' jacent to a slit comprises a straight part near the being less than one-fourth the radial spread of a wing in the said blade sheet.

-that portion and a relatively longer concaved 11. A fan-blade unit as per claim 5, in which the said clamping means comprise a stem having its rearward portion bored for attachment to a rotating shaft and having a peripheral flange at the forward-end of its said rearward portion, the stem member also having a second part extending forwardly from the said flange and through all of the said perforations; a washer larger in diameter than the said spacer member and interposed between the said fiange'and the spacer member, against which washer the central portion of the sheet bears rearwardly; and a forward element threaded upon the forward end of the said second part of the stem'member and bearing rearwardly against the most forward of the said straps. r

12. In a rotatable fan-blade unit, a rigid stem adapted to have its rear end fastened to a rotating shaft and having a peripheral flange intermediate of its ends; a blade-forming sheet of flexible rubber having a perforation in its center, through which perforation the part of the stem forward of the said enlarged portion extends forwardly; the said sheet having its central portion bearing rearwardly against the said flange and having equally spaced slits extending radially into it-to divide it into counterpart blade wing portions,

each such blade wing portion having a relatively narrow strap-like portion adjacent to its rotation ally outer edge and having a perforation near the free end of the said strap-like-portion; the said wing portions being consecutively recurved forwardly and radially inward of the said sheet' to dispose the said strap perforations in alinement with the central perforation in the sheet and to permit the said forward part of the stem to extend consecutively through the said wing perforations; a tubular spacer interposed between the said central portion of the sheet and the wing portions having the said wing perforations, through whichspacer the said forward part of the said stem also extends; and clamping means associated with the forward end portion of the said stem for simultaneously clamping the said perforated strap portions against the spacer and clamping the spacer against the forward face of the enlargement on the said stem.

13. A fan-blade unit as per claim 5, in which the clamping means comprise a forwardly tapering nut threaded upon the forward end of the said stem.

14. A fan-blade unit as per claim 12, in which the radius of the said enlargement on the stem approximately equals the distance between the center of the said sheet and the inner 'end of each of the said slits.

15. A fan-blade unit as per claim 5, in which the said means include a clamping element bearwardly from the said enlargement and through all of the said perforations; and a forward clamp.- ing element threaded upon the forward end of the last named part of the stem member-and bearing rearwardly against the most forward one of the said straps.

16.In a rotatable fan-blade .unit, a shaftattachable stem member having a peripheral flange intermediate its ends; a blade forming sheet of flexible rubber having a central perforation through which the said stem member extends, and having its central portion bearing rearwardly against the said flange; the said sheet having equally spaced radial slits dividing it into i portion of the said sheet and the said overlapping strap ends, and means simultaneously clamping the said overlapping strap ends against the spacer and clamping the spacer rearwsrdly against the said central sheet portion.

17. A rotatable fan-blade unit comprising a horizontal stem formed at its rear end for attachment to a shaft and having a peripheral enlargement intermediate its ends; a flexible rubber sheet having a central perforation through which the forward part of the said stem slidabiy extends, the said sheet having two pairs of alined slits extending into it approidmately to the periphery of the said enlargement and respectively along lines diametric of the said stem and at right angles to each other to define four counterpart wings; a rigid spacer bearing rearwardly against the central portion of the said sheet; the said wings having the parts thereof adjacent to the similarly rotationally facingslit edges recurved forwardly and thereafter toward the axis of the said stem so as to present the wing tips adJacent to these slit edges in relatively overlapping relation in front of the said spacer; and means mounted on the said stem and bearing rearwardly against the said overlapping wing tips for clamping the said tips, the spacer and the central portion of the said sheet coniointly against the said enlargement.

' EDWARD S. PRESTON. 

